If your going to use cables from the old PSU with the new one, take the 24 pin and jump it so the PSU will turn on then check the voltage on the cables just to make sure. Just because the cable fits does not mean that they didn't change where the voltage comes out on the plug.
I know for a fact Silverstone changed there PCI-e plugs from model to model and using and old cable would have put 12v on the ground to a video card. Im not saying corsair changed the pin out on the PSU but you never know.
Did you know that you can plug an 8 pin PCI-e cable into an 8pin cpu power connecter, guess what it wont boot up a computer like that, so your "If the socket at the psu end is identical then the cable will work" actually does not work.